In a small bowl, whisk together the olive oil, balsamic vinegar, Dijon mustard, honey, salt, and black pepper to make the dressing.
Layer the ingredients in the mason jars, starting with the dressing at the bottom, followed by cucumbers, red onion, olives, feta, and cherry tomatoes.
Top with mixed greens and seal the jars tightly.
Store the mason jars in the refrigerator for up to 4 days. When ready to eat, shake the jar to mix the dressing with the ingredients.
Notes
This salad can be easily customized with other vegetables, proteins, or nuts for added variety.